Personal Cooling System

ABSTRACT

A personal cooling system operates by pumping liquid through a garment. Because the personal cooling system pumps liquid, the compression system that generates the cooling power does not require the use of a condenser. The compression system utilizes a compression wave. An evaporator of the cooling system operates in the critical flow regime in which the pressure in an evaporator tube will remain almost constant and then ‘jump’ or ‘shock up’ to an increased pressure.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part and claims the priority benefit of U.S. patent application Ser. No. 12/732,171, filed Mar. 25, 2010, and U.S. provisional application No. 61/384,649 filed Sep. 20, 2010. U.S. patent application Ser. No. 12/732,171 claims the priority benefit of U.S. provisional application No. 61/163,438, filed Mar. 25, 2009, and U.S. provisional application No. 61/228,557, filed Jul. 25, 2009. The disclosure of each of the aforementioned applications is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to cooling systems. The present invention more specifically relates to personal cooling systems.

2. Description of the Related Art

A vapor compression system as known in the art generally includes a compressor, a condenser, and an evaporator. These systems also include an expansion device. In a prior art vapor compression system, a gas is compressed whereby the temperature of that gas is increased beyond that of the ambient temperature. The compressed gas is then run through a condenser and turned into a liquid. The condensed and liquefied gas is then taken through an expansion device, which drops the pressure and the corresponding temperature. The resulting refrigerant is then boiled in an evaporator. This vapor compression cycle is generally known to those of skill in the art.

FIG. 1 illustrates a vapor compression system 100 as might be found in the prior art. In the prior art vapor compression system 100 of FIG. 1, compressor 110 compresses the gas to (approximately) 238 pounds per square inch (PSI) and a temperature of 190° F. Condenser 120 then liquefies the heated and compressed gas to (approximately) 220 PSI and 117° F. The gas that was liquefied by the condenser 120 is then passed through the expansion valve 130 of FIG. 1. By passing the liquefied gas through expansion valve 130, the pressure is dropped to (approximately) 20 PSI. A corresponding drop in temperature accompanies the drop in pressure, which is reflected as a temperature drop to (approximately) 34° F. in FIG. 1. The refrigerant that results from dropping the pressure and temperature at the expansion valve 130 is boiled at evaporator 140. Through boiling of the refrigerant by evaporator 140, a low temperature vapor results, which is illustrated in FIG. 1 as having (approximately) a temperature of 39° F. and a corresponding pressure of 20 PSI.

The cycle related to the system 100 of FIG. 1 is sometimes referred to as the vapor compression cycle. Such a cycle generally results in a coefficient of performance (COP) between 2.4 and 3.5. The coefficient of performance, as reflected in FIG. 1, is the evaporator cooling power or capacity divided by compressor power. It should be noted that the temperature and pressure references that are reflected in FIG. 1 are exemplary and illustrative.

FIG. 2 illustrates the performance of a vapor compression system like that illustrated in FIG. 1. The COP illustrated in FIG. 2 corresponds to a typical home or automotive vapor compression system—like that of FIG. 1—operating in an ambient temperature of (approximately) 90° F. The COP shown in FIG. 2 further corresponds to a vapor compression system utilizing a fixed orifice tube system.

Such a system 100, however, operates at an efficiency rate (i.e., COP) that is far below that of system potential. To compress gas in a conventional vapor compression system 100 like that illustrated in FIG. 1 typically takes 1.75-2.5 kilowatts for every 5 kilowatts of cooling power generated. This exchange rate is less than optimal and directly correlates to the rise in pressure times the volumetric flow rate. Degraded performance is similarly and ultimately related to performance (or lack thereof) by the compressor 110.

Haloalkane refrigerants such as tetrafluoroethane (CH₂FCF₃) are inert gases that are commonly used as high-temperature refrigerants in refrigerators and automobile air conditioners. Haloalkane refrigerants have also been used to cool over-clocked computers. These inert, refrigerant gases are more commonly referred to as R-134 gases. The volume of an R-134 gas can be 600-1000 times greater than the corresponding liquid.

In light of the theoretical efficiencies of systems using haloalkanes or other fluids, there is a need in the art for an improved cooling system that more fully recognizes system potential and overcomes technical barriers related to compressor performance.

SUMMARY OF THE CLAIMED INVENTION

The personal cooling system disclosed herein includes a garment, the garment including a cooling fluid circulation path to carry cooling fluid throughout the garment. The cooling fluid circulation path may include a manifold coupled to a cooling fluid supply. The cooling fluid circulation path may include one or more branches coupled to the manifold.

The system further includes at least one pump that maintains the flow through the cooling fluid circulation path and a fluid flow path. The system also includes an evaporator that operates in the critical flow regime of the circulatory fluid in the fluid flow path. The evaporator generates a compression wave that shocks the maintained fluid flow, thereby changing the pressure of the maintained fluid flow and exchanging heat introduced into the circulatory fluid flow. No heat is added to the circulatory fluid flow before the circulatory fluid flow passes through the evaporator. The evaporator may use one or more tubes/nozzles, and may generate approximately 300 watts of cooling power at 38° C. ambient.

A heat exchanging mechanism may be thermally coupled to the fluid flow path. The heat exchanging mechanism may utilize at least a portion of an external surface of the control pack to vent heat to the atmosphere via convection from the surface. The heat exchanging mechanism may include one or more vents. A plurality of fins may be employed in the vents.

A control pack may be mounted on the body of the user. A thermostat may be included in the control pack to control the temperature of the system. The control pack may further include a battery, and a solar cell that may be used to power the system or to recharge the battery.

Operating conditions within the system may include the pump raising the pressure of the circulatory fluid flow from approximately 20 PSI to approximately 100 PSI. In certain embodiments, the pressure may be raised to pressures in excess of 100 PSI, such as 300 or 500 PSI.

A personal cooling system according to the technology disclosed herein may include a pump that maintains a fluid flow of a compressible fluid through the system, and an evaporator that effects a phase change in the compressible fluid. The system may establish a compression wave in the compressible fluid by passing the compressible fluid from a high pressure region to a low pressure region, the velocity of the fluid being greater than or equal to the speed of sound in the compressible fluid. The compressible fluid is cooled during a phase change so that heat may be transferred from the system by thermally coupling one or more fins between the compressible fluid and the ambient atmosphere.

Operating conditions in the evaporator may include a pressure drop in the cooling liquid to approximately 5.5 PSI. A corresponding phase change results in a lowered temperature of the cooling liquid. The pressure change may occur within a range of approximately 20 PSI to 100 PSI, or the increased pressure may be in excess of 100 PSI, such as 300 or 500 PSI.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a vapor compression system as might be found in the prior art.

FIG. 2 illustrates the performance of a vapor compression system like that illustrated in FIG. 1.

FIG. 3 illustrates an exemplary cooling system in accordance with an embodiment of the present invention.

FIG. 4 illustrates an exemplary cooling system in accordance with another embodiment of the present invention.

FIG. 5 illustrates performance of a cooling system like that illustrated in FIGS. 3 and 4.

FIG. 6 illustrates the operation of a single tube cooling system.

FIG. 7 illustrates an embodiment of a personal cooling system mounted on the back of a user.

FIG. 8 illustrates an embodiment of a personal cooling system mounted on the leg of a user.

FIG. 9 illustrates an embodiment of a personal cooling system utilizing a tight fitting garment.

FIG. 10 illustrates a method of operation for a personal cooling system.

DETAILED DESCRIPTION

FIG. 3 illustrates an exemplary cooling system 300 in accordance with an embodiment of the present invention. The cooling system 300 does not need to compress a gas as otherwise occurs at compressor 110 in a prior art vapor compression system 100 like that shown in FIG. 1. Cooling system 300 operates by pumping liquid. Because cooling system 300 pumps liquid, the compression cooling system 300 does not require the use of a condenser 120 as does the prior art compression system 100 of FIG. 1. Compression cooling system 300 instead utilizes a compression wave. The evaporator of cooling system 300 operates in the critical flow regime where the pressure in an evaporator tube will remain almost constant and then ‘jump’ or ‘shock up’ to the ambient pressure.

The cooling system 300 of FIG. 3 recognizes a heightened degree of efficiency in that the pump 320 of the system 300 is not required to draw as much power as the compressor 110 in a prior art compression system 100 like that illustrated in FIG. 1. A compression system designed according to an embodiment of the presently disclosed invention may recognize exponential performance efficiencies. For example, a prior art compression system 100 as illustrated in FIG. 1 may require 1.75-2.5 kilowatts to generate 5 kilowatts of cooling power. Prior art compression system 100 therefore may operate at a coefficient of performance (COP) of less than 3. A system 300 like that illustrated in FIG. 3 may pump fluid from approximately 14.7 to approximately 120 PSI with the pump drawing power at approximately 500W (0.5 kilowatts), with the system 300 also generating 5 kilowatts of cooling power. The system 300 may therefore operate with a COP of 10. As a result of the cycle illustrated in FIG. 3, and the resultant increased efficiencies, system 300 may utilize many working fluids, including but not limited to water.

The cooling system 300 of FIG. 3 may include a housing 310. Housing 310 of FIG. 3 is akin to that of a pumpkin. The particular shape or other design of housing 310 may be a matter of aesthetics with respect to where or how the system 300 is installed. The design of the housing 310 may be influenced by the facility in which the system 300 is installed, or by the equipment or machinery to which the system 300 is coupled. Functionally, housing 310 encloses pump 330, evaporator 350, and the attendant accessory equipment or flow paths (e.g., pump inlet 340 and evaporator tube 360). Housing 310 also contains the cooling fluid to be used by the system 300.

Housing 310, in an alternative embodiment, may also encompass a secondary heat exchanger as in system 400 (illustrated in FIG. 4). The secondary heat exchanger is not necessarily contained within the housing 310. In such an embodiment, the outer surface area of the system 400—that is, the housing 310—may be utilized in a cooling process through forced convection on the external surface of the housing 310.

Pump 330 may be powered by a motor 320, which may be external to the system 300 and is located outside the housing 310 in FIG. 3. Motor 320 may alternatively be contained within the housing 310 of system 300. Motor 320 may drive the pump 330 of FIG. 3 through a rotor drive shaft with a corresponding bearing and seal or magnetic induction, whereby penetration of the housing 310 is not required. Other motor designs may be utilized with respect to motor 320 and corresponding pump 330 including synchronous, alternating (AC), and direct current (DC) motors. Other electric motors that may be used with system 300 include induction motors; brushed and brushless DC motors; stepper, linear, unipolar, and reluctance motors; and ball bearing, homopolar, piezoelectric, ultrasonic, and electrostatic motors.

Pump 330 establishes circulation of a compressible fluid through the interior fluid flow paths of system 300, the flow paths being contained within housing 310. Pump 330 may circulate fluid throughout system 300 through use of vortex flow rings. Vortex rings operate as energy reservoirs whereby added energy is stored in the vortex ring. The progressive introduction of energy to a vortex ring via pump 330 causes the corresponding ring vortex to function at a level such that energy lost through dissipation corresponds to energy being input.

Pump 330 also operates to raise the pressure of a liquid being used by system 300 from, for example, 20 PSI to 100 PSI or more. Some systems may operate at an increased pressure of approximately 300 PSI. Other systems may operate at an increased pressure of approximately 500 PSI.

Pump inlet 340 introduces a liquid to be used in cooling and otherwise resident in system 300 (and contained within housing 310) into pump 330. Fluid temperature may, at this point in the system 300, be approximately 95 F.

The fluid introduced to pump 330 by inlet 340 traverses a primary flow path to nozzle/evaporator 350. Evaporator 350 induces a pressure drop (e.g., to approximately 5.5 PSI) and phase change that results in a low temperature. The cooling fluid further ‘boils off’ at evaporator 350, whereby the resident liquid may be used as a coolant. For example, the liquid coolant may be water cooled to 35-45° F. (approximately 37° F. as illustrated in FIG. 3).

As noted above, the system 300 (specifically evaporator 350) operates in the critical flow regime, thereby generating a compression wave. The coolant fluid exits the evaporator 350 via evaporator tube 360 where the fluid is ‘shocked up’ to approximately 20 PSI because the flow in the evaporator tube 360 is in the critical regime. In some embodiments of system 300, the nozzle/evaporator 350 and evaporator tube 360 may be integrated and/or collectively referred to as an evaporator.

The coolant fluid of system 300 (having now absorbed heat for dissipation) may be cooled at a heat exchanger to assist in dissipating absorbed heat, the temperature of the fluid being approximately 90-100° F. after having exited evaporator 350. Instead of a heat exchanger, however, the housing 310 of the system 300 (as was noted above) may be used to cool via convection. FIG. 5 illustrates an exemplary performance cycle of a cooling system like that illustrated in FIGS. 3 and 4.

FIG. 6 shows the operation of a cooling system 600 which may be utilized in the personal cooling system. Cooling system 600 utilizes the supersonic cooling cycle illustrated in FIGS. 3 and 4, and may typically be implemented in an embodiment requiring a cooling power of, for example, 300 watts. The system 600 utilizes a small pump 610 and at least one evaporator nozzle or tube 620. The tube 620 functions as the evaporator in the system 600. FIG. 6 illustrates a system 600 in which a single evaporator tube 620 is utilized. In various configurations of the system 600, more than one evaporator tube may be employed (as illustrated in FIGS. 3 and 4) depending on the requirements of a given application.

A heat exchanger 630 may be employed in a fluid flow path in the system 600 to remove heat from the system. The heat exchanger 630 is utilized in the transfer of heat away from the body of the user of the system.

The pump 610 raises the pressure of a fluid in the system 600. Various fluids, including water, may be used in the system. Refrigerants such as green refrigerant R134a may also be used. The pressure of the fluid may be raised from 20 PSI to in excess of 100 PSI. The fluid flows through the nozzle or tube 620 of the evaporator. Pressure drop and phase change result in a lower temperature of the fluid in the tube 620 and provide the cooling power for the system 600.

Critical flow rate, which is the maximum flow rate that can be attained by a compressible fluid as that fluid passes from a high pressure region to a low pressure region (i.e., the critical flow regime), allows for a compression wave to be established and utilized in the critical flow regime. Critical flow occurs when the velocity of the fluid is greater or equal to the speed of sound in the fluid.

In critical flow, the pressure in the channel will not be influenced by the exit pressure and at the channel exit, the fluid will ‘shock up’ to the ambient condition. In critical flow the fluid will also stay at the low pressure and temperature corresponding to the saturation pressures.

In cooling system 600, the cooled fluid is passed through heat exchanger 630 to effectuate a heat transfer to the atmosphere. The operating steps of the system 600 are described in further detail below with reference to FIG. 10.

FIG. 7 shows an exemplary embodiment of a personal cooling system 700. FIG. 7 illustrates a full body garment 710 used in an implementation of the personal cooling system 700. It will be recognized by those skilled in the art that the garment chosen may cover any part of the body chosen by the user. Suitable garments for various configurations of the personal cooling system 700 include, but are not limited to, full body garments such as overalls or jumpsuits, vests, shirts, pants, and hats. In short, any part of the body that the user desires to cool may be matched to a garment utilizing the personal cooling system 700.

The garment 710 of the cooling system 700 includes a cooling fluid circulation path 920 (see FIG. 9) thermally coupled to the fluid flow path of the working fluid of the supersonic cooling cycle of the system. The cooling fluid circulation path 920 carries cooling fluid throughout the garment. As the cooling fluid flows through the cooling fluid circulation path 920, the cooling fluid is subject to warming due to ambient and body heat. In systems utilizing a full body garment, warming of the fluid in the cooling fluid circulation path 920 can be a significant problem. Therefore, the cooling fluid circulation path 920 may be a manifolded capillary system to reduce the length of any given branch in the system. Minimizing the lengths of the branches in the cooling fluid circulation path 920 reduces the possibility of the cooling fluid absorbing too much heat to properly cool the user.

A control pack 720 may include a thermostat to control the temperature of the system. The system will typically be operated to maintain a temperature in the garment of between 12° C. and 24. C. The thermostat controlled operating temperature of the system ensures a comfortable and uniform temperature throughout the system. The control pack 720 may also include an on/off switch that controls the power supply to the system 700. The user may control the temperature in the cooling system 700 by simply turning the power on and off as necessary to maintain a comfortable temperature.

Heat may be vented from the system via vents 730 in the surface of the control pack 720. The vents 730 may be a series of fins to increase the surface area available for heat transfer. The vents may also be holes, slots, or any other construction that would facilitate the transfer of heat.

Personal cooling system 700 may be powered by a 12 or 24 volt power supply. The personal cooling system 700 may be powered by self-contained batteries or by a solar cell. A solar cell may also be used to charge the self-contained batteries. Those skilled in the art will recognize that many power supply configurations may be utilized in the personal cooling system 700.

As depicted in FIG. 7 personal cooling system 700 may have the control pack 720 mounted on the back of the user, akin to a backpack. However, the position in which the control pack 720 is mounted may vary with a given application. The mounting of the control pack 720 is a matter of choice of the user of the system. The system may be mounted on the back as shown in FIG. 7 or on the leg as shown in FIG. 8. The control pack 720 may be mounted at any location on the garment 710 that is convenient for the user.

FIG. 9 illustrates a personal cooling system 900 that utilizes a tight fitting garment 910. Garment 910 may be made from a stretchable fabric such as Spandex, Lycra, etc., to hold the cooling fluid in the cooling fluid circulation path 920 in close proximity to the body of the user.

A manifolded cooling fluid supply 930 routes cooling fluid cooled by the working fluid in the fluid flow path through the cooling fluid circulation path 920. The cooling fluid circulation path 920 is thermally coupled to the fluid flow path of a supersonic cooling cycle. The cooling fluid circulation path 920 may trace, as illustrated in FIG. 9, the main arteries of the body of the user. Positioning the cooling fluid circulation path 920 so that it traces the main arteries of the user may increase the efficiency of heat dissipation from the body of the user.

Personal cooling system 900 combines the tight fitting garment 910 with a cooling fluid circulation path 920 that traces the main arteries of the user. Users of the system 900 may therefore experience improved efficiency of heat removal due to the system 900 maintaining close contact between the cooling fluid in the circulation path 920 and areas of significant heat accumulation from the body of the user, i.e. the main arteries.

FIG. 10 illustrates a method of operation 1000 for the cooling cycles utilized in the systems disclosed herein. In step 1010, a pump raises the pressure of a liquid. The pressure may, for example, be raised from 20 PSI to in excess of 100 PSI. As mentioned above, the increased pressure may be 300 PSI or even 500 PSI. In step 1020, fluid flows through the nozzle/evaporator tube(s). Pressure drop and phase change result in a lower temperature as fluid is boiled off in step 1030.

Critical flow rate, which is the maximum flow rate that can be attained by a compressible fluid as that fluid passes from a high pressure region to a low pressure region (i.e., the critical flow regime), allows for a compression wave to be established and utilized in the critical flow regime. Critical flow occurs when the velocity of the fluid is greater or equal to the speed of sound in the fluid. In critical flow, the pressure in the channel will not be influenced by the exit pressure and at the channel exit, the fluid will ‘shock up’ to the ambient condition. In critical flow the fluid will also stay at the low pressure and temperature corresponding to the saturation pressures. In step 1040, after exiting the evaporator tube, the fluid “shocks” up to 20 PSI. A heat exchanger may be used in optional step 1050. Cooling may also occur via convection on the surface of the housings of the systems 300, 400.

While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. The descriptions are not intended to limit the scope of the invention to the particular forms set forth herein. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments. It should be understood that the above description is illustrative and not restrictive. To the contrary, the present descriptions are intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims and otherwise appreciated by one of ordinary skill in the art. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents. 

1. A personal cooling system comprising: a garment including a cooling fluid circulation path to carry a cooling fluid throughout the garment, the circulation path being thermally coupled to a fluid flow path; a pump that maintains a fluid flow of a working fluid through a fluid flow path, the pump also maintaining flow of the cooling fluid through the cooling fluid circulation path; an evaporator that operates in the critical flow regime of the working fluid and generates a compression wave that shocks the maintained fluid flow in the fluid flow path, thereby changing the pressure of the maintained fluid flow to cool the fluid; a heat exchanging mechanism to transfer heat from the system.
 2. The personal cooling system of claim 1, further comprising a control pack, the control pack including a battery to power the system.
 3. The personal cooling system of claim 1, further comprising a control pack, the control pack including a thermostat to control the temperature of the system.
 4. The personal cooling system of claim 1, further comprising a control pack, the control pack including a solar cell to charge the battery.
 5. The personal cooling system of claim 1, further comprising a control pack, an external surface of the control pack including at least one vent.
 6. The personal cooling system of claim 5, wherein the heat exchanging mechanism comprises a plurality of fins to increase the surface area of the heat exchanging mechanism.
 7. The personal cooling system of claim 1, wherein a single tube is utilized in the evaporator.
 8. The personal cooling system of claim 1, wherein the evaporator generates approximately 300 watts of cooling power.
 9. The personal cooling system of claim 1, further comprising a manifold coupling a cooling fluid supply to the cooling fluid circulation path, the cooling fluid circulation path including one or more branches coupled to the manifold.
 10. The personal cooling system of claim 1, wherein the garment is made from a stretchable fabric fitted to hold the cooling fluid circulation path in close proximity to the body of a user.
 11. The personal cooling system of claim 1, wherein the cooling fluid circulation path traces major arteries of the body of a user.
 12. A personal cooling system comprising: a garment including a cooling fluid circulation path thermally coupled to a fluid flow path; a pump that maintains a fluid flow of a compressible working fluid through a fluid flow path and through the cooling fluid circulation path; and an evaporator that effects a phase change in the compressible working fluid, wherein the evaporator establishes a compression wave in the compressible working fluid by passing the compressible working fluid from a high pressure region to a low pressure region, the velocity of the fluid being greater than or equal to the speed of sound in the compressible working fluid, the compressible working fluid being cooled during a phase change, the cooled working fluid cooling the cooling fluid in the fluid circulation path, thereby cooling the user of the personal cooling system.
 13. The system of claim 12, wherein the garment is made from a stretchable fabric fitted to hold the cooling fluid circulation path in close proximity to the body of a user.
 14. The system of claim 12, wherein the working fluid is water.
 15. The system of claim 12, wherein the evaporator induces a pressure drop in the working fluid to approximately 5.5 PSI, a corresponding phase change resulting in a lowered temperature of the working fluid.
 16. The system of claim 12, wherein a pressure change within the fluid flow of the compressible working fluid occurs within a range of approximately 20 PSI to 100 PSI.
 17. The system of claim 12, wherein a pressure change within the fluid flow of the compressible working fluid involves a change to an excess of 100 PSI.
 18. The system of claim 12, wherein cooling fluid circulation path traces major arteries of the body of a user.
 19. The system of claim 12, wherein the pump raises the pressure of the fluid flow from approximately 20 PSI to approximately 100 PSI.
 20. The system of claim 12, wherein the pump raises the pressure of the fluid flow to more than 100 PSI. 